In broad terms an application server is an information system that provides the run-time environment for applications.
Generally speaking, the applications hosted by application servers handle transactions between an organisation's database servers and/or back and business applications and any end users or clients who wish to access those resources.
FIG. 1 shows a simplified scenario in which one or more clients 110 may access central computing resources 120 via an application server 130. A client may be, for example, a workstation operating under appropriate operating system and application software. Client requests may require the application server to access one or more resources, for example an object database 120A, a relational database 120B, or an external application 120C. This type of arrangement may be satisfactory for a small business with centralised resources which several employees need to access from their workstations.
However, in today's environment, especially with the popularity of the Internet and a growing array of other wireless and telecommunications networks, more and more organisations are offering services to consumers over traditional WAN's, wireless network and wireline networks via an application server. These services could include, for example, access to a private database over the Internet or in the context of the telecommunications services call forwarding services from a client's home phone to mobile phone or voice mail access. Consumers of such services are creating a high demand for new services that integrate features from the Internet, wireless and wireline networks. Application server technology is becoming increasingly complex to keep pace with these consumer demands.
There is considerable pressure for application servers to be highly available, highly scalable, fault tolerant, and to facilitate the rapid development of next generation services for clients and consumers. It would be useful to have a distributed application server that was highly scalable, fault tolerant, portable and standardised and that was suitable for service provisioning in an integrated network.